Paper making machine



p 1962 c. G. R. JOHNSON 3,052,039

PAPER MAKING MACHINE Filed Nov. 29, 1957 5 Sheets-Sheet 1 F 1- HVVENTUR.

CHARLES G RUSSELL JOHNSON JWffornegs Sept. 4, 1962 G JOHNSON 3,052,039

PAPER MAKING MACHINE Filed Nov. 29, 1957 3 Sheets-Sheet 2 )INVENTOR.CHARLES G. RUSSELL JOHNSON Sept. 4, 1962 c. G. R. JOHNSON 3, ,039

PAPER MAKING MACHINE Filed Nov. 29, 1957 3 Sheets-Sheet 3 INVENTOR.CHARLES G. RUSSELL JOHNSON 12W, ju n 3,952,039 Patented Sept. 4, 19623,052,039 PAPER MAKING MACHlNE Charles G. Russell Johnson, Neenah, Wis.,assignor to Kimberly-Clark Corporation, Neenah, Wis, a corpora tion ofDelaware Filed Nov. 29, 1957, Ser. No. 699,704 15 Claims. (Cl. 34-110)This invention relates to a welded pressure vessel and more particularlyto a welded wrought drum drier for use in the manufacture of paper andto a method of fabricating the same.

The dry creping of paper tissue is usually carried out with a Yankeetype paper machine. In this type of machine, the wet paper web, afterbeing couched from the forming wire and partially de-watered betweenfelts, is pressed on to the surface of a large heated cylindrical drierand dried to the desired final moisture content within a singlerevolution of the drier. The dried paper web is removed from the surfaceof the drier by a doctor blade which rides on the drier surface. TheYankee type paper machine differs from that of a conventionalFourdrinier paper machine in that the Fourdrinier machine contains alarge number of small driers and the paper is transferred from one drierto another by a series of rolls and canvas carriers.

The Yankee driers are cast or welded structures and generally have adiameter of 8 to 15 feet, a length of 10 to feet and weight in theneighborhood of 65 or 70 tons. During operation, the drum driers aresubjected to both internal and external pressures. One or severalpressure rolls bear against the external surface of the drier at thepoint where the wet sheet is first applied. These pressure rolls exert aforce of from 200 pounds to 450 pounds gr more per lineal inch acrossthe entire face length of the men In addition to this external pressure,a heating medium, such as steam under high temperatures and pressures,is introduced into the interior of the drier and serves to dry the paperweb on the outer surface of the drier.

The temperature and pressure of the steam or other heating media andthus the drying rate are regulated by the code limitations for the drieritself. As the rate of heat transfer through the shell of thecylindrical drier is generally inversely proportional to the shellthickness, increasing the thickness of the shell to permit higher steampressures and temperatures reduces the heat transfer through the shelland this, to an extent, nullifies the increased heating eflfect of thehigher temperature steam. These factors generally determine thethickness of the drum drier shell and limit the operation of the castdrier shell, particularly those of the Yankee type, to operational steampressures of less than 165 psi Rolled or wrought materials, because oftheir increased mechanical properties over the cast material, permit theconstruction of thinner drying shells than a cast structure and therebywill result in a substantially higher rate of heat transfer.

While the use of a welded wrought structure will generally increase theproduction range over that of a similar cast structure, the weldedstructures present certain operational difficulties. While the weldeddrier shell is subjected to heat treatment techniques in an attempt tominimize the differences in mechanical properties between the parentmetal and the Weld areas, it has not been possible to provide the weldareas with identical properties to that of the parent metal. In view ofthe slight difierences in mechanical properties between the weld areasand the parent or base metals, certain differences in the operationalcharacteristics of the welded drum drier result.

The inner and outer surfaces of the drum drier shell are ground ormachined to a desired degree of smoothness and tolerance to insure auniform wall thickness for heat transfer and to permit the drier torotate at high speeds. If a welded joint in the drier shell extendsparallel to the axis of the shell, the doctor blade which rides on thesurface of the rotating shell and is parallel to the axis of the drieris apt to abrade or gouge the shell surface due to the slight differencein wear resistance and hardness between the weld metal and the parentmetal, and thereby cause chattering of the blade and non-uniformity ofoperation.

Furthermore, as the coefiicient of thermal expansion of the weld areaand the parent metal may differ slightly, distortion of the cylindricalsurface of the drier may result due to the difierence in temperature.

During operation, the inner surface of the shell is subjected to the hotsteam while the outer surface is cooled by the wet paper web and thisdifierence in temperature is apt to cause distortion and loss ofconcentn'city in the cylindrical shell when the weld areas and theparent metal have different coefficients of thermal expansion. Anydistortion in concentricity of the drier shell will cause uneven contactof the doctor blade and poor running of the pressure roll.

The weld metal and the parent metal also have slight differences intensile strength and elongation properties. If the welded joint isparallel to the axis of the drier, the deflection of the shell as itpasses under the pressure roll will vary and this will cause variationsin nip pressure and operating problems. In addition, if the welded jointis parallel to the axis of the drier, the cyclic stressing of the drieras the drier rolls past the heavy pressure roll nip will be substantial.

The present invention is directed to a welded drum drier shell in whichthe difficulties occurring because of the difference in mechanicalproperties between the weld area and the parent metal are minimized.According to the invention, the welded drum drier shell is fabricatedsuch that the welds between the shell plates are disposed diagonally, atan angle greater than 5 to the axis of the drier shell. With thisconstruction, the doctor blade and pressure roll will not bear on theentire weld seam at one time but will ride progressively along thediagonal seam as the drier rotates.

The diagonal weld pattern of the drier shell of the invention eliminatesdoctor blade gouging and chattering and uneven wear of the drier shellwhich are apt to occur in a conventional welded drier shell due to thedifferences in wear resistance and hardness between the welded jointsand the parent metal.

Furthermore, the structure of the invention minimizes distortion of thedrier shell due to the differences in thermal expansion and thermalconductivity between the weld areas and the parent metal. Any distortionin the cylindrical shell is confined to the area of a diagonal weld anddoes not extend continuously along an element of the shell or radiallyaround its circumference, and

this limited distortion is readily bridged by the pressure roll nip withgreatly improved running of the drier.

As the weld seams extend diagonally or spirally, an entire weld seamdoes not pass under the pressure roll at a given time but instead, thepressure roll rides progressively along the weld seam. This minimizesthe deflection of the drier shell and the magnitude of the cyclicstresses and results in a more uniform operation.

In the diagonally welded structure, the stress pattern is improved as nosingle weld is subjected to the entire hoop stress. The diagonallywelded pattern also simplifies the manufacture of large diameter shellsas it is easier to maintain a true cylindrical shape by welding spiraljoints than by welding along an element parallel to the axis of theshell or around the circumference in a plane normal to the axis of theshell.

Other objects and advantages will appear in the course of the followingdescription.

The drawings illustrate the best mode presently contemplated of carryingout the invention.

In the drawings:

FIGURE 1 is a fragmentary side elevation of a paper making machineincorporating the drum drier of the invention;

FIG. 2 is a fragmentary end view of the drum drier structure shown inFIGURE 1;

FIG. 3 is a longitudinal section of the drum drier;

FIG. 4 is a top plan view of a plate from which the drum drier isfabricated, showing the cutting of the plate into two segments;

FIG. 5 is a view similar to FIG. 4 showing two plate segments weldedtogether to form a parallelogram-shaped section;

FIG. 6 is a view similar to FIG. 4 showing the sections welded togetherto form the plate pattern;

FIG. 7 is a perspective view of the completed welded shell; and

FIG. 8 is a perspective view of a second embodiment of the inventionshowing a modified form of the welded pattern.

The drawings illustrate a typical Yankee type paper machine whichincludes a supporting frame 1 which rests on a suitable foundation 2 androtatably supports a drum drier 3. The wet paper web is adapted to beapplied to the outer surface of the drum drier shell and during -asingle revolution of the drum drier, the paper web is dried and removedor scraped from the drier surface by a creping doctor.

The drum drier includes a generally cylindrical welded shell 4 havingend flanges 5 which are bolted to heads 6. The heads 6 enclose the endsof the shell and are provided with aligned axial openings which receivethe hollow shaft 7. The shell may be fabricated from any desired metalor alloy having the necessary mechanical properties for service, such assteel, aluminum, bronze or the like.

The drum drier is mounted for rotation by providing the ends of theshaft 7 with journals 8 which are rotatably supported in bearings 9secured to frame 1.

The shaft 7 is formed of two hollow, axially aligned sections 10 and 11which are separated by a separator plate 12. The separator plate 12 isprovided with a thickened rim 13, and a series of openings 14 extendthrough the rim and communicate with the interior of the shell 4. Steamnozzles 15 are threaded into the openings 14 and serve to distributesteam from the interior 16 of the shaft section 10 to the interior ofthe shell 4.

To remove the steam condensate from the drier, a pair of scoops 17 aresecured to the ends of pipes 18 which extend radially through openings19 in the shaft section 11. The inner ends of the pipes 18 are connectedto a conduit 20 which extends outwardly through the passage 21in shaftsection 11 to the exterior. With this construction, the scoops 17' serveto scoop up the steam conden- 4 sate from the interior of thecylindrical shell 4 and discharge the same through the conduit 20 to theexterior.

The drum drier 3 is rotated by a conventional drive mechanism, notshown, which is attached to the end of the shaft 7 by a suitable gear orpulley arrangement.

To provide additional heat to dry the paper web on the surface of theshell 4, a heating hood 22 is secured to frame 1 and extends around theupper portion of the shell 4. Suitable hot air inlets and outlets areprovided in the hood for the entry and discharge of the air or otherheating medium.

The wet paper web to be dried is carried by a felt web 23 which travelsaround felt rolls 24. The paper web is forced against the surface of thedrier shell 4 by a pressure roller 25 which is rotatably mounted inbrackets 26 attached to arm 27. The arm 27 is pivoted at 28 to the frame1 and the pressure roller 25 is forced against the surface of the driershell 4 by a ram 29 of a hydraulic cylinder 30 which bears against thearm 27.

The dried paper web is removed from the surface of the drier shell by acreping doctor, which includes a doctor blade 31 which is removablysecured within the doctor blade holder 32. The ends of the holder 32 areprovided with shafts 33 which are rotatably mounted within guide blocks34. The blocks 34, in turn, are each slidably mounted within a slideassembly 35 attached to pivot frame 36 pivotally carried by frame 1.Through the slide arrangement provided by guide blocks 34 and slideassembly 35, the vertical position of the doctor blade 31 can be varied,as desired, to obtain the best creping angle.

The doctor blade holder 32 and blade 31 are pivoted by a togglemechanism 37 which is attached through lever arm 38 to one of the shafts33. In addition, a spring loading mechanism 39 is connected through thetoggle mechanism 37 to provide a resilient contact for the doctor bladeagainst the surface of the drier shell 4.

In addition to the vertical and pivotal adjustment for doctor blade 31,the doctor blade is adapted to oscillate in a direction generallyparallel to the axis of the shell 4. The oscillating m tion is providedby an eccentric drive, shown generally at 40, which is connected to oneof the shafts 33. The oscillating motion is permitted by a loose fitbetween the pivot frame 36 and frame 1 and permits the doctor blade tomove back and forth across the shell surface as the shell rotates toprevent uneven wear of the doctor blade and of the drier duringoperation.

According to the invention, the drier shell 4 is fabricated from aseries of generally rectangular rolled plates 41. As shown in FIG. 4,the rectangular plates 41 are initially cut diagonally at 42 to providetwo halves or segments 43 and 44. The cut at 42 is made so as to dividethe rectangular plate 41 into two generally equal segments of similarshape and surface area. The angle of the cut 42 with respect to thelongitudinal side edge of the plate is greater than 5 and preferablywithin the range of 30 to 60". It has been found that 45 is the optimumangle of the cut 42 in order to provide the completed shell with minimumwear, maximum strength, freedom from distortion and general stressbalance.

After severing the rectangular plates into the segments 43 and 44, theedges of the segments are scarfed for welding and the segments arereversed in position so that the square ends of the segments are inabutting relation. The aligned ends of the segments are welded togetherat 45 to provide a generally parallelogram-shaped section 46, as shownin FIG. 5.

A series of the parallelogram-shaped sections 46 are then arranged withthe diagonal edges in alignment and the longitudinal side edges inopposed relation, as shown in FIG. 6, to form a larger plate pattern.The number of sections 46 in the pattern depend upon the diameter of theshell to be fabricated. The abutting side edges of the sections 46 arethen welded together, as at 47.

The large parallelogram-shaped pattern is then rolled into cylindricalform and the free ends are welded along line 48 to provide the generallycylindrical welded structure shown in FIG. 7.

After welding, the cylindrical shell 4 is heat treated to minimize thedifferences in mechanical properties between the plates and the weldseams and then fitted to the component parts of the drier. The inner andouter surfaces of the drier shell are then machined to provide a uniformwall thickness for heat transfer.

For the fabrication of smaller diameter shells, it is contemplated thatthe parallelogram-shaped pattern can be formed as a single piece and thefree ends can then be welded as at 48 to provide the cylindrical shellhaving a single diagonal Weld.

Each of the welds 45, 47 and 48, as best shown in FIG. 7, is disposed atan angle greater than 5 to the axis of the shell. With thisconstruction, the doctor blade 31, which bears on the surface of theshell, will not contact the entire weld seam at one particular time inthe rotation of the shell, but the contact area between the blade andthe weld will instead ride along the generally spiral weld seam. Withthis welded pattern, the blade 31 will be in contact with at least oneof the weld seams at any given time during the rotation of the shell.

The welded wrought drier shell of the invention serves to substantiallyminimize the difiiculties encountered by the difference in physicalproperties between the parent metal and the weld seams.

As the weld seams extend diagonally to the axis of the shell and thedoctor blade rides progressively along the seam, the wear on the shellsurface will be substantially uniform. This uniformity of wear iscritical in that the drier shell concentricity must generally bemaintained within a tolerance of plus or minus 0.003 inch. This highdegree of precision is necessary to maintain the desired crown anduniform pressure contact across the face of the drier shell and also topermit uniform creping of the sheet from the shell surface. If localizedwear causes portions of the shell surface to fall outside of this 0.003inch limit, the drier shell surface must be reground at a substantialexpense and loss of production.

In addition, the girth or hoop stress in a vessel subjected to internalpressure is approximately twice that of the longitudinal stress and thusa vessel having a longitudinal weld seam is designed to accommodate thehoop stress. However, with the diagonal welds in which there are nowelds subjected completely to hoop stress, the maximum tensile stress towhich a weld is subjected, perpendicular to the course of the weld, isless than the hoop stress and thus the welds can be designed for lessermaximum tensile stresses. In view of this, a weld pattern in which allof the welds extend at an angle of 45 to the axis of the shell, providesthe optimum mechanical properties and the greatest freedom fromdistortion. With 45 welds, all of the Welds are subjected to theidentical internal stresses, and a symmetry of stress is obtained.

The welded pattern of the invention greatly improves the generalbalance, uniformity of Wear, freedom from distortion and the uniformityof internal stress in a drier shell.

FIG. 8 shows a second embodiment of the invention having a modifiedwelding pattern. In this embodiment, the cylindrical shell 4 isfabricated from a plurality of rings 49 and a pair of wedge-shaped endsections 50 which are welded to the outer end of the rings 49.

Each of the rings 49 is a continuous member, and the ends of each ringlie in parallel planes extending at an angle greater than 5 to the axisof the ring. As shown in FIG. 8, the opposed ends of rings 49 are joinedtogether by welds 51 and welds 52 join the tapered end sections 50 tothe outer ends of the respective rings. The welds 51 and 52 are allpositioned at an angle greater than 5 to the axis of the shell, as inthe case of the first embodiment.

To insure uniform wear of the doctor blade and the shell surface, anygiven point on the doctor blade should be contacted by at least one ofthe welds 51 and 52 during rotation of the shell in operation.

While the above description is directed to a Yankeetype drum drier, itis contemplated that the Welded shell of the invention can be employedin any situation where a rotating shell is subjected to the action of apressure member, scraping blade or the like. This includes driers foruse in all creping operations, such as dry creping, semi-creping and wetcreping, for in each case, including the manufacture of machine glazedpaper, the drier is subjected to the scraping action of either a crepingdoctor or a cleaning doctor. The welded shell of the invention isadapted to withstand a wide range of internal and external stresses.Moreover, it may be used with various heating or cooling media, such ashot vapors, including steam, gases, products of combustion and liquidssuch as oil, heat stabilized ortho di chloro benzene or similarcompounds, molten metal, brine and the like.

Various modes of carrying out the invention are contemplated as beingwithin the scope of the following claims particularly pointing out anddistinctly claiming the subject matter which is regarded as theinvention.

I claim:

1. In a pressure vessel, the combination of a rotatable generallycylindrical welded shell having a weld seam extending at an acute anglegreater than 5 to the axis of said shell, and a member extending in aplane substantially parallel to the axis of the shell and disposed inengagement with the outer surface of said shell and adapted to ride onsaid surface as the shell is rotated.

2. In a drying apparatus, a generally cylindrical welded shellfabricated from a plurality of wrought plates joined together by aseries of welds with all of the welds of said series extending at anangle of 30 to 60 to the axis of the shell, means for mounting the shellfor rotation about the axis thereof, and a pressure member extendingsubstantially the length of said shell in a plane substantially parallelto the axis of said shell and disposed to ride on the outer surface ofthe shell as the same rotates.

3. In a drum drier for use in a paper making machine, a generallycylindrical welded shell fabricated from a plurality of wrought platesjoined together by a series of welds, said plates all havingsubstantially the same surface area and said welds all extending atsubstantially the same angle in the range of 30 to 60 to the axis of theshell, and a member extending substantially the length of said shell ina plane substantially parallel to the axis of the shell and disposed toride on the outer surface of the shell as the same rotates.

4. In a pressure vessel, a generally cylindrical shell adapted to besubjected to substantial internal pressure in service and composed of aplurality of rolled plates joined together by a series of welded joints,means for mounting the shell for rotation about the axis thereof, and anexternal pressure member disposed to ride on the outer surface of theshell as the shell is rotated, said pressure member being disposed in aplane substantially parallel to the axis of said shell and said Weldedjoints being disposed at an acute angle to the axis of said shell ofsuflicient magnitude to effect engagement of the pressure member with atleast one of said welded joints at any given time during the rotation ofsaid shell.

5. In a pressure vessel, a generally cylindrical shell adapted to besubjected to substantial internal pressure in service and composed of aplurality of rolled plates joined together by a series of welded jointsextending diagonally to the axis of said shell, a pair of headsenclosing the ends of the shell, means associated with the heads formounting the shell for rotation about the axis thereof, and a blademember disposed in engagement with the outer surface of the shell andadapted to ride thereon as the shell is rotated, said blade memberdisposed in a plane substantially parallel to the axis of said shell andextending substantially the length of said shell, said welded jointsbeing disposed at an acute angle to the blade member and spaced withrelation to each other to eifect engagement of the blade member with atleast one of said joints at any given time during the rotation of saidshell.

6. In a drum drier for use in a paper making machine, a generallycylindrical rotatable drier shell adapted to receive a web of wet paperon the outer surface thereof and dry the web as the shell is rotated,said shell including a plurality of generally parallelogram-shapedsections with each section having a pair of opposite longitudinal sideedges and a pair of diagonal end edges With the corresponding diagonalend edges of adjacent sections being disposed in alignment and theadjacent side edges of said sections being Welded together to provide anintegral cylindrical structure, and a doctoring blade disposed inbearing engagement with the outer surface of the shell and adapted toscrape the paper web from said shell as the shell is rotated, saiddoctoring blade disposed generally parallel to the axis of the shell andextending substantially the length of the shell.

7. In a drum drier for use in a paper making machine, a generallycylindrical rotatable drier shell adapted to receive a Web of wet paperon the outer surface thereof and dry the web as the shell is rotated,said shell including a plurality of generally parallelogram-shapedsections with each section having a pair of opposite longitudinal sideedges and a pair of diagonal end edges with the corresponding diagonalend edges of adjacent sections being disposed in alignment and theadjacent side edges of said sections being in opposed relation, a seriesof welds joining the opposed side edges of adjacent sections to providean integral cylindrical structure, and a doctoring rnenrber disposed inengagement with the outer surface of the shell and disposed in a planeextending generally parallel to the axis of said shell, said doctoringmember adapted to ride on the surface of the shell as the same isrotated to scrape the web from the shell.

8. In a drum drier for use in a paper making machine, the combination ofa rotatable generally-cylindrical welded shell adapted to receive a webof wet paper on the outer surface thereof and to dry the web as theshell is rotated, said shell having at least one weld seam extending atan acute angle greater than to the axis of the shell, and a doctoringmember disposed in bearing engagement with the outer surface of theshell and adapted to scrape the paper web from the surface of the shellas the shell is rotated, said doctoring member disposed generallyparallel to the axis of the shell and extending substantially the lengthof the shell.

9. In a drum drier for use in a paper making machine, a generallycylindrical rotatable drier shell adapted to receive a web of wet paperon the outer surface thereof and dry the web as the shell is rotated,said shell including a cylindrical central section having the oppositeends thereof lying in substantially parallel planes disposed at an anglegreater than 5 with respect to the axis of said section and said shellhaving a generally wedgesh-aped end section welded to each end of saidcentral section with the outer end of each wedge-shaped section lying ina plane extending substantially perpendicular to the axis of said shell,and a doctoring blade disposed in bearing engagement with the outersurface of the shell and adapted to scrape the paper web from said shellas the shell is rotated, said doctoring blade disposed generallyparallel to the axis of the shell and extending substantially the lengthof the shell.

10. In a drum drier for use in a paper making machine, a generallycylindrical rotatable drier shell adapted to receive a Web of wet paperon the outer surface thereof and dry the web as the shell is rotated,said shell including a series of concentric rings welded endwisetogether to form a central section with the outer ends of the centralsection lying in substantially parallel planes disposed at an angle of30 to 60 to the axis of the shell and said shell having a generallytapered end section welded endwise to each outer end of said centralsection With the outer end of each tapered section lying in a planeextending substantially perpendicular to the axis of said shell, and adoctoring blade disposed in bearing engagement with the outer surface ofthe shell and adapted to scrape the paper web from said shell as theshell is rotated, said doctoring blade disposed generally parallel tothe axis of the shell and extending substantially the length of theshell.

11. In a drum drier for use in a paper making ma chine, a generallycylindrical rotatable drier shell adapted to receive a web of Wet paperon the outer surface thereof and dry the web as the shell is rotated,said shell including a plurality of sections with each section having apair of first generally parallel edges and a pair of second generallyparallel edges disposed at an acute angle to said first pair of edges,the corresponding first edges of adjacent sections being disposed inalignment and the adjacent second edges of said sections being weldedtogether to provide an integral cylindrical structure, and a pressuremember disposed in bearing engagement with the outer surface of theshell, said pressure member disposed generally parallel to the axis ofthe shell and extending substantially the length of the shell.

12. In a drum drier for use in a paper making machine, a generallycylindrical rotatable drier shell adapted to receive a web of wet paperon the outer surface thereof and dry the web as the shell is rotated,said shell including a plurality of quadrangular sections with eachsection having a pair of opposite first edges and a pair of oppositesecond edges with said second edges disposed at an angle of 30 to 60with respect to said first edges, the corresponding first edges ofadjacent sections being disposed in alignment and the adjacent secondedges of said sections being disposed in abutting relation and 'WCldedtogether to provide an integral cylindrical structure, and a pressuremember disposed in engagement with the outer surface of the shell anddisposed in a plane extending generally parallel to the axis of theshell, said pres sure member adapted to ride on the surface of the shellas the same is rotated.

13. In a drum drier, a generally cylindrical shell having a smoothmachined outer surface adapted to receive a web of paper and dry the webas the shell is rotated, said shell being fabricated from a plurality ofplates joined together by a series of Welds with said welds allextending at an acute angle to the axis of said shell, said angle beingof sufficient magnitude to effect engagement of a pressure memberextending substantially parallel to the axis of the shell with at leastone of the welds at any given time during rotation of the shell,journalling means for mounting the shell for rotation about the axisthereof, and means associated with said journalling means for supplyinga heating medium to the interior of the shell.

14. A drum drier structure, comprising a generally cylindrical shellhaving a smooth machined outer surface adapted to receive a Web of Wetpaper and dry the web as the shell is rotated, said shell beingfabricated from a plurality of plates joined together by a series ofwelds with all of said welds extending at an angle in the range of 30 to60 to the axis of the shell, a head enclosing each end of the shell, andjournalling means associated with the heads for mounting the shell forrotation about the axis thereof, said journalling means having a firstopening for introducing steam into the interior of the shell and saidjournalling means having a second opening for withdrawing condensatefrom the shell.

15. In a drum drier, a generally cylindrical rotatable drier shelladapted to receive a web of wet paper on the outer surface thereof anddry the web as the shell is rotated, said shell including a plurality ofplates of substantial thickness each of which is in the form of aparallelogram with the ends extending on a bias with respect to thesides, said sides of the plates being Welded together to form thecylindrical shell With the ends of the plates forming the ends of theshell and with the sides of the plates forming seams extendingdiagonally across the shell from one end of the shell to the other,means for mounting the shell for rotation about the axis thereof wherebya pressure member disposed generally parallel to the axis of the shellis adapted to ride on the outer surface of the shell as the same isrotated, and means for supplying a heating medium to the interior of theshell to dry the web of paper thereon.

References Cited in the file of this patent UNITED STATES PATENTS SmithDec. 2, 1919 Wood Sept. 19, 1933 Hansen July 10, 1934 Milne Aug. 14,1934 Smith July 27, 1937 Overton June 27, 1944 Fischer Sept. 12, 1950Fergusson June 17, 1952 Henchert Dec. 16, 1952 Hornbostel June 30, 1959

